Bone cutter

ABSTRACT

A bone milling tool for precise preparation of bones includes a milling head connected to a driveshaft. The driveshaft simultaneously serves as a guide element which is guided in a bone. The bone milling tool further includes a toothing which is arranged on the milling head facing the driveshaft.

FIELD OF THE INVENTION

The invention relates to a bone milling tool for precise preparation of.

BACKGROUND OF THE INVENTION

From the DE-OS 27 48 452 is known a bone milling tool for round millinga hip joint head which is provided with a central hole into which acentering pin is inserted. The milling head is joined to a driveshaftwhich is,. at least near the area of the milling head, of tubulardesign.

Also known is a bone milling tool as illustrated in FIG. 4. A bonemilling tool of this type is used for precisely fitting preparation ofbones, in particular tubular bones. It is important, in particular withcementfree implantation of prosthesis, to create an extremely preciselyfitting bone bed to accommodate the prosthesis, on the one hand toensure the largest possible contact surface for fast grafting of thebone and on the other hand to eliminate micro movements. Rotaryinstruments are preferred as the precision of oscillating saws isinsufficient.

Bone milling tool 10a illustrated in FIG. 4 is a front-end milling tool.It is composed of a cylindrical milling head 12a with cutting teethconfigured at the front. A guide pin 30 is also arranged at this side. Adriveshaft 14' is mounted to the rear of milling head 12a. When usingthis bone milling tool 10a, guide pin 30 is pushed into a guide borewhich has been entered into the bone, thus ensuring guided anddirectionally stable processing. Exerting pressure (see arrows 26 inFIG. 4) onto driveshaft 14' in the direction of guide pin 30 establishescontact of front-end cutting teeth with the bone and mills arotary-symmetrical surface into the depth.

The problem with both of the aforedescribed bone milling tools lies withthe respective driveshaft, which protrudes from the field of operationand has to be connected to a drive unit. If the field of operation issmall and access has to be of narrow design for anatomical or surgicalreasons, then it can happen that, whilst milling downwards, thedriveshaft is forced out of its direction by protrusions in the field ofoperation, which results in a directionally unstable or directionallyincorrect milling surface. The result is an inaccurate bone bed, bothrelative to the contact surface and relative to positioning of aprosthesis.

SUMMARY OF THE INVENTION

It is an object of the invention to create a bore milling tool whichmakes it easily possible to establish a bone bed of maximum fittingaccuracy even in the event of a small field of operation.

An aspect of the invention involves a bone milling tool for precisepreparation of bones. The bone milling tool includes a milling headconnected to a driveshaft. The driveshaft simultaneously serves as aguide element which is guided in a bone. The bone milling tool furtherincludes a toothing which is arranged on the milling head facing thedriveshaft.

According to the invention, the driveshaft simultaneously serves asguide element and is passed through a continuous guide bore which isestablished in the bone. As the toothing is arranged at the side of thedriveshaft on the milling head, work is, in contrast to conventionalbone milling tools, no longer carried out by pushing but by pulling.

When using the bone milling tool, the driveshaft extends from themilling head in the direction of the bone and through the guide borewhich has been established in the latter. The driveshaft then no longerprotrudes from the field of operation and can no longer be forced out ofits direction by objects which protrude into the field of operation.This ensures production of a bone bed of high fitting accuracy.

The driveshaft is preferably of flexible design. The use of a flexibledriveshaft is only made possible because work is no longer carried outby pushing but by pulling.

According to a further advantageous embodiment, a guide pipe is insertedinto the guide bore which has been established in the bone. Thedriveshaft then no longer rubs against the bone or adjacent soft parts.The guide pipe can be pushed thereinto from the end of the bore locatedopposite the field of operation. When lowering the milling work, themilling head pushes the guide pipe in front of it without milling it.

As the driveshaft has to be guided all the way through the bone, and asit has to be connected on one side to the milling head and on the otherside to a drive unit, at Least one of these connections has to be ofdetachable design. The detachable connection is preferably provided atthe point of transition from driveshaft to milling head or at the pointof transition from driveshaft to drive unit.

In the first case, the driveshaft is prior to milling inserted from theopposite end of the guide bore in the direction of the field ofoperation and connected to the milling head. In the second case, thedriveshaft is pushed from the field of operation through the guide boreand on exit from the bone on the opposite side connected to the driveunit.

The milling head can be of varying design, but should berotary-symmetrical. For cylindrical milling, a milling head is chosen,the toothing of which is configured in one plane. This produces a planecutting surface standing perpendicularly to the driveshaft.Alternatively, a milling head can be used which comprises a cuttingsurface which is concave, convex or a combination of such surfaces. Thisallows milling of spherical, conical, cylindrical, polygonal, wavy orany other rotary-symmetrical shape surfaces.

A preferred embodiment is characterised in that the cutting surface isextended by a non-cutting protective collar. The protectice collar keepssoft parts away from the milling zone.

The toothing of the milling head can be of conventional design, i.e. itcan be milled or hammered. However, particularly advantageous is the useof a rasplike toothing with additional waste-removal holes provided inthe milling head. This makes it possible to remove bone waste from themilling area.

A special combination of the latter embodiment of a toothing isestablished when a catching device, in particular a collecting vessel,is arranged at the rear of the milling head. For example, the use of asmall basket or dishlike container in which occurring bone waste can becollected, would be useful. This can not only prevent pollution of thefield of operation by such waste and reduce the danger of an inducedundesirable ectopic bone growth, but additional waste collected in thecontainer can be used further as valuable autologem spongiosa pulp.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in more detail, also in view offurther advantages and features, based on exemplary embodiments and withreference to the enclosed drawings. The drawings show in

FIG. 1 a diagrammatical side view of an exemplary embodiment of theinventive bone milling tool;

FIG. 2 a cross-sectional illustration of a further form of embodiment ofthe inventive bone milling tool with domeshaped cutting surface andscrew connection between milling head and driveshaft;

FIG. 3 a diagrammatical perspective illustration of a third form ofembodiment of an inventive bone milling tool with rasplike toothing andcollecting container; and

FIG. 4 a diagrammatical side view of a bone milling tool of the priorart.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates an exemplary embodiment of a bone milling tool 10b,consisting essentially of a cylindrical milling head 12b and adriveshaft 14.

Milling head 12b has at its surface facing toward driveshaft 14 atoothing 20b which is, in the present exemplary embodiment, milled.However, it can also be hammered or arranged in a different manner. Allteeth of toothing 20b lie essentially in one plane, so that its useproduces a cutting surface which extends perpendicularly to driveshaft14.

Driveshaft 14 is firmly connected to milling head 12b and serves at thesame time as guide element corresponding with guide bolt 30 of FIG. 4.To allow use of bone milling tool 10b, initially a continuous guide borehas to be established in the bone. For example, to shape a hip jointhead by milling, the continuous guide bore is introduced through theshank neck. Driveshaft 14 is pushed from the direction of the shank headthrough the guide bore and on exit from the bone at the lateral sideconnected to a drive unit (not illustrated).

In the present bone milling tool 10b, guide bolts and driveshaft 14coincide and toothing 20b is not arranged at the end surface but at therear (similar to the lamellae of a mushroom), so that bone milling tool10b does not operate by means of pushing on driveshaft 14 but by pullingthe latter (see arrows 28). This makes it possible to also operate witha flexible driveshaft 14.

When working with a flexible driveshaft, it is of advantage to line theguide bore laterally with a guide pipe (not illustrated), so that rotarydriveshaft 14 does not rub against the bone or adjacent soft parts. Whenworking downwards, milling head 12b simply pushes the guide pipe aheadof itself without milling it.

FIG. 2 illustrates a further exemplary embodiment of a bone milling tool10c, and the same reference numbers correspond with identical parts.Bone milling tool 10c differs from the one of FIG. 1 in two ways.

For one, milling head 12c is of domeshaped design as can be seen in thecross-sectional illustration. A concave cutting surface with respectivetoothing 20c is provided at the side of milling head 12c which isassociated with driveshaft 14. This permits milling a shape surfacewhich corresponds with said surface. The cutting surface is extended bya protruding, non-cutting protective collar 32 in order to keep softparts away from the cutting zone.

Furthermore, driveshaft 14 and milling head 12c are detachably joinedtogether, i.e. by means of a bolt 18. The latter is passed through acentered bore 16 in milling head 12c and is screwed into an insidethread at the side of the milling head of driveshaft 14. With a bonemilling tool 10c of this type, driveshaft 14 is prior to a millingoperation entered laterally from the end of the guide bore in thedirection of the shank head and then connected to milling head 12c bymeans of bolt 18.

A third embodiment of a bone milling tool 10d is illustrated in FIG. 3.This bone milling tool 10c offers special qualities relative to theaforedescribed forms of embodiment, in particular the one of FIG. 1.Toothing 20d at the driven surface of milling head 12d is of rasplikedesign and comprises waste removing holes 22 which extend throughmilling head 12d. Above the surface of milling head 12d oppositedriveshaft 14 is arranged a removable collecting vessel 24, so that allbone waste severed by raspshaped toothing 20d and transported throughwaste remov ng holes 22 can be caught in said collecting vessel 24. Thiseffectively prevents pollution of the field of operations thus limitingthe danger of induced, undesirable ektopic bone growth. Bone wastecaught in the removable collecting vessel 24 can subsequently beprocessed further into a valuable autologem spongiosa pulp.

In all, the described embodiments show bone milling tools by means ofwhich a precisely fitting bone bed, for example for accommodatingprostheses, can be created without elements of the bone milling toolprotruding from the field of operation and making contact with objectsin the field of operation. A directionally unstable or directionallyincorrect milling surface can be effectively avoided.

Bone milling tools that are coated with hard material provide producemilled bone surfaces which distinguish themselves in that they bondcompletely with hydroxialpatit layered implant surface, for examplewithin 10 and 14 days. This allows considerable acceleration in healingof implants.

Reference List

10a, b, c, d--Bone Milling Tool

12a, b, c, d--Milling Head

14--Driveshaft

14'--Driveshaft of the Prior Art

16--Bore

18--Bolt

20b, c, d--Toothing

22--Waste Removing Holes

24--Collecting Vessel

26--Arrow (symbolising Pushing Load)

28--Arrow (symbolising Pulling Load)

30--Guide Bolt

32--Protective Collar

What is claimed is:
 1. A bone milling tool for precise preparation ofbones, comprising:a milling head; a flexible driveshaft detachablyconnected to the milling head and configured to serve simultaneously asa guide element which is guided in a bone; and a toothing arranged onthe milling head facing the driveshaft.
 2. A bone milling tool forprecise preparation of bones, comprising:a milling head; a flexibledriveshaft connected to the milling head and configured to servesimultaneously as a guide element which is guided in a bone; and atoothing arranged on the milling head facing the driveshaft.
 3. A bonemilling tool for precise preparation of bones, comprising:a millinghead; a driveshaft connected to the milling head and configured to servesimultaneously as a guide element which is guided in a bone; a guidepipe configured to be placed in the bone and to receive the driveshaftin a rotary mounted manner; and a toothing arranged on the milling headfacing the driveshaft.
 4. The bone milling tool of claim 1, wherein thedriveshaft has a connection configured to detachably connect to a driveunit.
 5. The bone milling tool of claim 1, wherein the milling head issymmetrical about an axis of rotation.
 6. The bone milling tool of claim5, wherein the milling head comprises a cutting surface having a shapeselected from a group including essentially plane, concave, convex, anda combination of concave, convex and plane surfaces, and wherein saidshape is prefixed.
 7. A bone milling tool for precise preparation ofbones, comprising:a milling head, wherein the milling head comprises acutting surface having a shape selected from a group includingessentially plane, concave, convex, and a combination of concave, convexand plane surfaces, a non-cutting protective collar which protrudes overthe milling head; a driveshaft connected to the milling head andconfigured to serve simultaneously as a guide element which is guided ina bone; and a toothing arranged on the milling head facing thedriveshaft.
 8. The bone milling tool of claim 1, wherein the toothing ofthe milling head is milled or hammered.
 9. A bone milling tool forprecise preparation of bones, comprising:a milling head; a driveshaftconnected to the milling head and configured to serve simultaneously asa guide element which is guided in a bone; and a toothing arranged onthe milling head facing the driveshaft, wherein said toothing israsplike with holes for the passage of milled bone.
 10. The bone millingtool of claim 9, further comprising a collecting device detachablyarranged on the milling head to collect bone waste which passes throughthe holes.
 11. The bone milling tool of claim 10, wherein the collectingdevice is configured as a collecting vessel.
 12. The bone milling toolof claim 11, wherein the collecting device is configured as a basket.13. The bone milling tool of claim 6, wherein the cutting surface of themilling toothing are coated with a hard material.
 14. The bone millingtool of claim 13, wherein the hard material is selected from a groupincluding diamond, carbide and nitride.